1. Field of the Invention
The invention generally relates to the techniques for handling random access failures, and more particularly, to apparatuses, systems, and methods for handling random access failures in a multi-carrier system.
2. Description of the Related Art
In order to meet users' demand for higher data rate in wireless communications, support of wider transmission bandwidths is required. A so-called Carrier Aggregation (CA) technique has been proposed to allow expansion of effective bandwidth delivered to a user terminal through concurrent utilization of radio resources across multiple carriers. The CA technique is most useful when it is difficult to derive a contiguous and extra wide bandwidth. With the CA technique, 2 or more frequency bands may be aggregated to form a larger transmission/receive bandwidth. Each of the aggregated frequency bands is generally referred to as a carrier frequency.
Specifically, each carrier frequency needs to be configured and activated before it may be used for data transmission or reception. The network side may first transmit a Radio Resource Control (RRC) message to configure the carrier frequencies for a Mobile Station (MS) (or may be referred to as a User Equipment), and then transmit a Medium Access Control (MAC) activation command to the MS to activate one of the carrier frequencies. After that, the MS may initiate a random access procedure on the activated carrier frequency for uplink timing alignment, requesting radio resources, or other purposes. If the MS is configured with more than one carrier frequency, there may be several random access procedure being concurrently performed or waiting to be performed on multiple carrier frequencies for the MS.